The present invention relates to a developing device with respect to electrostatic latent images, in which non-magnetic toners of mono-component are provided on the electrostatic latent images to be made visible. The developing device of the invention may be applied to an electrographic copying machine, or a recording machine for electrostatic latent images.
There is known a mono-component developing method in which a thin layer of charged toners uniformly formed on a toner transport member is brought into contact with a photosensitive member or a photoreceptor to develop electrostatic latent images (e.g. Japanese Patent Laid-Open No. 143831/1977).
There are many systems for a mono-component developing method. In principle, a cylindrical toner-transport member is set between a photoreceptor drum on which electrostatic latent images are formed and a mono-component toner container. A toner-levelling member, which plays a role in charging toners, is pressed against the toner transport member. Toners are charged positively or negatively to an adequate level while passing through between the toner transport member and the toner levelling member. At the same time, a thin layer of charged toners is formed on the toner transport member and the toners are transported to the photoreceptor and attracted electrostatically to electrostatic latent images on the photoreceptor to be made visible.
It is important for a mono-component developing system in a developing method to provide the surface of a toner transport member with a thin layer of charged toners. Particularly, it is necessary to form an homogeneous layer on a toner transport member with respect to both charge amount and layer thickness. The uniformity of toners on the toner transport member is an important element which influences image qualities directly.